Metalworking apparatus and metalworking method

ABSTRACT

A pressing portion ( 11 ) formed in a tapered conical shape pushes away a metallic material of a to-be-opened portion ( 5 ) radially outward from the radial center. A portion pushed away ( 2   b ) is work-hardened (base-material-hardened) and a density of the plate material ( 2 ) increases as compared to that of the other portion of the plate material ( 2 ). A radial dimension (c 2 ) of a work-hardened portion at a peripheral edge of the to-be-opened portion ( 5 ) is larger than a radial dimension (c 1 ) of the pressing portion ( 11 ) (c 1 &lt;c 2 ).

TECHNICAL FIELD

The present invention relates to a metalworking apparatus and a metalworking method.

BACKGROUND ART

A conventional metalworking apparatus that forms a hole in a metal plate by a shear-punching method using a punch and a die has been known (see Patent Literature 1 or the like, for example). In such an apparatus, the punch has an edge with a curved surface and a distal end with a conically recessed surface. This ensures that the shear cut surface of the hole does not crack or fracture.

PRIOR ART REFERENCE Patent Document

-   Patent Literature 1: JP2002-120025A

SUMMARY OF INVENTION Problem to be Solved

With conventional metalworking tools, rollover occurs by which a curve is radially formed at a peripheral edge of a punched hole. Also, in the case of boring a plurality of holes adjacently to each other, a metallic material between the holes sinks in, and thereby causes material drag.

Thus, there has been a demand for a further improvement to reduce rollover and material drag.

An object of the present invention is to provide a metalworking apparatus and a metalworking method capable of reducing rollover and material drag.

Means to Solve the Problem

A metalworking apparatus of the present invention includes a forging tool configured to work-harden a to-be-opened portion of a workpiece through forging, and a punching tool configured to form an opening portion in the to-be-opened portion by punching. The punching tool has an insertion portion that has a diameter equal to a diameter of the opening portion, and a shoulder portion which is joined to the insertion portion and has a diameter which is larger than a diameter of the insertion portion and increases as the shoulder portion extends toward a proximal end of the punching tool. When forming the opening portion by punching, the punching tool is inserted to such a position that the shoulder portion contacts a work-hardened portion remaining at an inner peripheral edge of the opening portion from an inner side surface.

Advantageous Effects of the Invention

According to the present invention, a metalworking apparatus and a metalworking method capable of reducing rollover and material drag are provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view of a main part, describing a forging step with a forging tool in a metalworking apparatus and a metalworking method in an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a main part, describing a punching step with a punching tool in the embodiment.

FIG. 3 is a schematic cross-sectional view of a main part, describing a striking step with a striking tool in the embodiment.

FIG. 4 is a schematic cross-sectional view of a main part of a metal plate, showing that an opening portion has been processed to be flat in the embodiment.

FIG. 5 is a plan view of a metal plate in which plural opening portions are disposed adjacently to one another in the embodiment.

FIG. 6 is a cross-sectional view of the metal plate, taken at a position along the VI-VI line of FIG. 5 in the embodiment.

FIG. 7 shows a comparative example and is a cross-sectional view of a metal plate taken at a position corresponding to that in FIG. 6 .

FIG. 8 is a side view of a main part, showing an example of the punching tool.

FIG. 9A shows a modification of the forging tool of the embodiment, and is a schematic cross-sectional view of a main part, showing that a metal plate is work-hardened through forging with a forging tool having a flat end surface.

FIG. 9B is a schematic cross-sectional view of a forging tool having a tapered conical distal end with no flat portion therearound, showing how to use it.

FIG. 9C is a schematic cross-sectional view of a forging tool having a flat end surface with an inclined surface formed by chamfering the outer peripheral edge of the flat end surface, showing how to use it.

EMBODIMENTS OF THE INVENTION

An embodiment of the present invention will be described below with reference to the drawings as appropriate. Identical constituent components are denoted by the same reference sign and overlapping description is omitted.

In a metalworking apparatus 1, a plate material 2, which is a workpiece, is fixed on a clamping jig not shown. In this state, steps are sequentially performed. The steps include a forging step of striking and thus forging a to-be-opened portion 5 to work-harden the to-be-opened portion 5, a punching step of forming an opening portion 3 in the forged to-be-opened portion 5 of the plate material 2 by punching, and a striking step of striking and flattening a small protrusion 6 appearing around the punched opening portion 3 with a striking tool.

Through these steps, the metalworking apparatus 1 of the present embodiment forms the plural opening portions 3 through the plate material 2 having a thin plate shape as shown in FIG. 5 in an out-of-plane direction. As a result, the plate material 2 turns into a plate-shaped product 4 in which the opening portions 3 having a 3×4 formation or total of 12 are formed in a matrix pattern at equal intervals both vertically and horizontally (see FIG. 5 ). In the present embodiment, the relation among the hole diameter, a plate thickness, and a pitch of the opening portions 3 is set such that the hole diameter is less than the plate thickness, and the pitch is less than or equal to three times the hole diameter.

Note that a case of forming a single opening portion 3 in the plate material 2 is mainly and exemplarily shown in the present embodiment for simple description. Descriptions for the other opening portions 3 are omitted, which are formed in a similar manner to the single opening portion 3.

First, a configuration of a forging tool 10 to be used in the forging step will be described.

The metalworking apparatus 1 is provided with the clamping jig not shown for horizontally placing and fixing the plate material 2, and a slide movement member. While the forging tool 10 is mounted on the slide movement member, the slide movement member moves the forging tool 10 along a slide direction (a vertical direction in FIG. 1 ).

The forging tool 10 is provided with a pressing portion 11 at a lower end portion, and a flat portion 12 located around the peripheral edge of the pressing portion 11.

The pressing portion 11 in the present embodiment has a distal end 11 a provided to protrude in a tapered conical shape such that the lowest point of the pressing portion 11 is on a central axis S at the center in the radial direction.

When the forging tool 10 is mounted on the slide movement member, the distal end 11 a of the pressing portion 11 faces the to-be-opened portion 5 of the plate material 2 horizontally fixed by the clamping jig. The to-be-opened portion 5 will be the opening portion 3 when the plate material 2 is completed as the plate-shaped product 4.

Then, as the slide movement member is moved downward in the slide direction, the conical distal end 11 a of the pressing portion 11 of the forging tool 10 comes into contact with a portion 2 a of the upper surface of the plate material 2 and presses the to-be-opened portion 5 from above.

The pressing portion 11, which is formed in a tapered conical shape, pushes away a metallic material presented in the to-be-opened portion 5 radially outward from the radial center. A portion 2 b thus pushed away is work-hardened (base-material-hardened) and a density of the plate material 2 increases as compared to that of the other portion of the plate material 2.

A radial dimension c2 of a work-hardened portion at the peripheral edge of the to-be-opened portion 5 is larger than a radial dimension c1 of the pressing portion 11 (c1<c2).

Also, the flat portion 12, which has an annular shape, is provided around the pressing portion 11 in the present embodiment. The flat portion 12 is provided to be parallel to the plate material 2 mounted on the clamping jig. When the plate material 2 is forged by the pressing portion 11, the flat portion 12 comes into contact with the peripheral edge of the to-be-opened portion 5 from above.

The flat portion 12 contacts the peripheral edge of the to-be-opened portion 5 and presses the plate material 2 downward from above in the out-of-plane direction toward the clamping jig supporting the plate material 2 from below. This prevents the metallic material at the peripheral edge of the to-be-opened portion 5 from moving upward in the out-of-plane direction, and thus promotes the work-hardening.

The metalworking apparatus 1 of the present embodiment includes a punching tool 20 to be used in the punching step, as shown in FIG. 2 . The punching tool 20 forms the opening portion 3 in the to-be-opened portion 5 of the plate material 2 by punching.

The punching tool 20 integrally has: a cylindrical insertion portion 22 located on a distal end (lower end) side and having a diameter substantially equal to the radial dimension c1 of the pressing portion 11 of the forging tool 10; a proximal end portion 24 on a proximal end (upper end) side being larger in diameter than the insertion portion 22 and mounted on the slide movement member to move with slide movement in the up-down direction; and a shoulder portion 26 provided between the insertion portion 22 and the proximal end portion 24 and joined to the upper side of the insertion portion 22 in the slide direction (up-down direction).

Of these, an inclination angle α2 of the shoulder portion 26 is smaller than an inclination angle α1 of the pressing portion 11 shown in FIG. 1 (α1>α2). In the present embodiment, α1=approximately 45 degrees, and α2=approximately 10 degrees.

As shown in FIG. 8 , a curved surface 28 is formed on the shoulder portion 26 in the present embodiment. The curved surface 28 is formed to gradually increase in diameter outward as the shoulder portion 26 extends from the insertion portion 22 toward the proximal end portion 24.

A rate of increase in diameter of the curved surface 28 (an increased dimension r in the radial direction/a dimension h in the slide direction) is set such that the rate gradually increases as the curved surface 28 extends from the insertion portion 22 toward the proximal end portion 24.

For example, assuming that sections of the curved surface 28 are given uniform dimensions in the slide direction (h1=h2=h3), the amount of increase in the radial direction increases gradually at each section (r1<r2<r3).

Thus, at the portion joined to the insertion portion 22, the curved surface 28 has the smallest rate of increase in diameter and is flush with the side surface of the insertion portion 22. Also, the curved surface 28 has the largest rate of increase in diameter at the portion joined to the proximal end portion 24.

As shown in FIG. 2 , the insertion portion 22 of the punching tool 20 is brought into contact with the work-hardened portion of the to-be-opened portion 5 to form the opening portion 3 by punching. At this time, it is preferable that the opening portion 3 is made within the work-hardened region in the to-be-opened portion 5.

When the insertion portion 22 of the punching tool 20 is inserted in the slide direction, the insertion portion 22 punches the plate material 2 toward its lower surface while leaving the metallic material which has an increased density and is work-hardened around the insertion portion 22.

When the shoulder portion 26 of the punching tool 20 comes into contact with an inner side surface 16 of the opening portion 3, the shoulder portion 26 pushes the metallic material around the peripheral edge of the opening portion radially outward while urging the metallic material to be pushed out upward from the opening portion 3.

Thus, the metallic material around the peripheral edge of the opening portion, which is urged to move downward in the slide direction by being dragged with the punching tool 20, remains at its current position. This reduces the occurrence of rollover and material drag at the peripheral edge of the opening portion 3.

Also, the metalworking apparatus 1 of the present embodiment includes a striking tool 30 to be used in the striking step, as shown in FIG. 3 . The striking tool 30 slides in the vertical direction along with the slide movement member to strike and flatten a small protrusion 6 appearing around the opening portion 3 from above.

For example, as shown in FIG. 2 , depending on the amount of insertion of the shoulder portion 26 when the opening portion 3 is punched with the punching tool 20, a small protrusion 6 protruding upward from the peripheral edge of the opening portion 3 may appear.

The striking tool 30 has a flat striking surface 32 on the lower side thereof facing the plate material 2.

The striking surface 32 is provided to be parallel to an upper surface 2 c of the plate material 2 fixed by the clamping jig, and is capable of evenly striking and flattening the small protrusion 6 appearing around the opening portion 3 by sliding the slide movement member downward.

The punching tool 20 is pulled out of the opening portion 3. By being struck with the striking tool 30 from above, the small protrusion 6 appearing around the opening portion 3 gets crushed to the same height as the upper surface 2 c, and thus becomes flat (see FIG. 4 ).

In the present embodiment, as shown in FIG. 5 , the plate-shaped product 4 is formed in which the opening portions 3 having a 3×4 formation or total of 12 are formed in a matrix pattern at equal intervals both vertically and horizontally.

In the punching step, as shown in FIG. 6 , the amount of movement of each slide movement member in the slide direction is controlled to adjust the amount of insertion of the corresponding punching tool 20 into the corresponding opening portion 3. For this reason, equipment capable of finely adjusting the dimension of insertion of the shoulder portion 26 is preferred. Also, the positional accuracy of the metalworking apparatus in the slide direction is desirably within ± 1/100 to 1/1000 mm. In this way, it is possible to adjust the pressing force of the shoulder portion 26 contacting the inner side surface 16 at the peripheral edge of the opening portion 3 and reduces the occurrence of the small protrusion 6.

FIG. 7 , in contrast, shows a comparative example in which a metal plate not having work-hardened is worked by using a normal punching tool having a straight insertion portion without the shoulder portion 26. In this comparative example, rollovers are formed at the peripheral edges of opening portions 3 a to 3 c. The sizes of such rollovers (hereinafter also referred to as rollover amounts d1, d2, . . . ) are larger at a portion where the plural opening portions 3 are formed (e.g., d1<d2). Here, the rollover amount d1 is approximately 0.1 mm, and the rollover amount d2 is approximately 0.15 mm.

In particular, when the opening portions 3 a to 3 c are arranged in a straight line, the rollover amounts d1, d2, . . . formed at the peripheral edges of the opening portions 3 a to 3 c are such that the rollover amount is piled up toward the intermediate position. Thus, at a region around the middle opening portion 3 b, the material drag occurs by which the region sinks downward by a predetermined dimension H from the surrounding upper surface 2 c. Here, the predetermined dimension H is approximately 0.05 mm.

Next, advantageous effects of the metalworking apparatus and the metalworking method in the embodiment will be described.

In the present embodiment, as shown in FIG. 1 , the to-be-opened portion 5 of the plate material 2 is work-hardened through forging with the forging tool 10.

Specifically, in the forging step with the forging tool 10 of the present embodiment, firstly, the forging tool 10 is mounted on the slide movement member. The distal end 11 a of the forging tool 10 is provided to protrude in a tapered conical shape on the central axis S at the center in the radial direction and is disposed immediately above a center portion of the to-be-opened portion 5.

As the slide movement member is moved downward in the slide direction, the pressing portion 11 moves downward to approach the plate material 2 which is fixed horizontally. The distal end 11 a is then brought into contact with the center of the to-be-opened portion 5 of the plate material 2.

As the slide movement member is further moved downward in the slide direction, the pressing portion 11 of the forging tool 10 pushes away the metallic material radially outward from the radial center which the distal end 11 a has contacted. The portion 2 b thus pushed away is work-hardened (base-material-hardened) and the density of the to-be-opened portion 5 increases as compared to that of the other portion of the plate material 2.

Here, since the pressing portion 11 of the present embodiment has the distal end 11 a provided to protrude in a conical shape, the metallic material pressed evenly in all radially outward directions from the central axis S is pushed away.

In addition, the conical pressing portion 11 of the forging tool 10 of the present embodiment is provided to protrude in a tapered shape. Thus, when the metallic material in the to-be-opened portion 5 is evenly pushed away, the metallic material gets compressed downward from the pressing portion 11. Also, since a large amount of the metallic material is evenly pushed away toward the radially outer surrounding region, the occurrence of cracking and the like is reduced. This makes it possible to obtain the to-be-opened portion 5 work-hardened with the radial dimension c2, which is larger than the outer radial dimension c1 of the pressing portion 11.

Note that, in the forging step, the clamping jig fixing the plate material 2 may have a concave portion recessed from the upper surface. It is more preferable that the concave portion be formed to be aligned with the central axis S.

In the forging step with the forging tool 10, the flat portion 12 prevents the metallic material at the peripheral edge of the to-be-opened portion 5 from escaping upward in the out-of-plane direction. This enables greater compression, so that the efficiency of the work-hardening is excellent.

As shown in FIG. 2 , the insertion portion 22 of the punching tool 20 is inserted into the work-hardened portion of the to-be-opened portion 5 to form the opening portion 3 by punching. The shoulder portion 26 of the punching tool 20 is brought into contact with the work-hardened portion remaining at the inner peripheral edge of the opening portion 3 from the inner side surface 16.

At this time, the amount of insertion of the punching tool 20 is adjusted to stop the force applied from the shoulder portion 26 to the inner side surface 16 immediately before the small protrusion 6 protrudes upward beyond the upper surface 2 c. This makes the peripheral edge of the opening portion 3 flush with the upper surface 2 c and hence improves the exterior quality.

Also, depending on the amount of insertion of the punching tool 20, the small protrusion 6 that has appeared may protrude upward from the peripheral edge of the opening portion 3.

In the present embodiment, the striking tool 30 is used to strike the small protrusion 6 protruding from the periphery from the opening portion 3 as shown in FIG. 3 . This forms a flat surface flush with the upper surface 2 c as shown in FIG. 4 .

Hence, it is possible to reduce the rollover and the material drag even if the metalworking apparatus 1 does not have an excellent positional accuracy of the slide movement member in the slide direction. Accordingly, the plate-shaped product 4 with desired exterior quality is obtained without increasing a manufacturing cost.

Also, as shown in FIG. 8 , the rate of increase in diameter of the curved surface 28 of the shoulder portion 26 (r/h) increases as the curved surface 28 extends from the insertion portion 22 on the distal end side toward the proximal end portion 24 on the proximal end side.

That is, the rate of increase in diameter is set smaller near the insertion portion 22 on the distal end side. Thus, even if the metalworking apparatus 1 does not have an excellent positional accuracy in the slide direction, the pressing force on the inner side surface 16 from the shoulder portion 26 does not change abruptly. It is therefore possible to use a metalworking apparatus with a slide movement member having a low positional accuracy in the slide direction, e.g., a metalworking apparatus with a positional accuracy of about 1/10 mm in the slide direction. This prevents an increase in manufacturing cost.

For example, with a curved surface 28 which has a rate of increase in diameter of r1/h1 (or r2/h2) lower than that of r2/h2 (or r3/h3), misalignment in the slide direction will cause only a small change in the amount of working of the opening portion 3.

Also, the rate of increase in diameter of the shoulder portion 26 on the proximal end portion 24 side is set to be higher than that on the insertion portion 22 side. This reduces the amount of change in cross-sectional area in a direction perpendicular to the central axis at the portion where the shoulder portion 26 is joined to the proximal end portion 24 to avoid providing a portion of a bent origin. This improves the support rigidity of the insertion portion 22 of the punching tool 20, and facilitates a work for a small opening portion 3.

Also, as shown in FIG. 3 , the striking tool 30 comes into contact with the flat striking surface 32 to strike and flatten the small protrusion 6 appearing around the opening portion 3.

Thus, even if the positional accuracy of the slide movement member in the slide direction is not high, a region surrounding the opening portion 3 is made flush with the other region of the upper surface 2 c of the plate material 2, as shown in FIG. 4 .

This reduces the rollover or the material drag and achieves a plate-shaped product 4 with a desired exterior quality.

FIGS. 9A to 9C show modifications of the forging tool in the embodiment. Note that portions identical or equivalent to those of the metalworking apparatus and the metalworking method of the embodiment are denoted by the same reference signs, and description thereof is omitted.

FIG. 9A shows a forging tool 40 of the modification. The forging tool 40 has a flat end surface 41 as a pressing surface. Moreover, the forging tool 40 work-hardens the plate material 2 through forging.

By the work-hardening, the to-be-opened portion 5 is pushed away radially outward from the radial center over a larger area than that of the embodiment to improve the density.

The other components and advantageous effects are identical or equivalent to those of the metalworking apparatus and the metalworking method of the embodiment, and description thereof is therefore omitted.

In FIG. 9B, the plate material 2 is work-hardened through forging with a forging tool 50 which has a pressing surface 51 having a tapered conical distal end and does not have a flat portion around the pressing surface 51 (see the flat portion 12 in FIG. 1 ).

With the forging tool 50 thus configured, the to-be-opened portion 5 is pushed away radially outward from the radial center to improve the density.

The other components and advantageous effects are identical or equivalent to those of the metalworking apparatus and the metalworking method of the embodiment, and description thereof is therefore omitted.

In FIG. 9C, the plate material 2 is work-hardened through forging with a forging tool 60 which has a flat end surface 61 with an inclined surface 62 formed at its outer peripheral edge by chamfering.

With the forging tool 60 thus configured, particularly an outer peripheral edge portion of the to-be-opened portion 5 is pushed away radially outward from the radial center to improve the density.

The other components and advantageous effects are identical or equivalent to those of the metalworking apparatus and the metalworking method of the embodiment, and description thereof is therefore omitted.

As described above, the metalworking method using the metalworking apparatus 1 of the present embodiment includes the forging step of work-hardening the to-be-opened portion 5 of the plate material 2 through forging (see FIG. 1 ) and the punching step of forming the opening portion 3 in the forged to-be-opened portion 5 of the plate material 2 by punching (see FIG. 2 ).

In this way, the to-be-opened portion 5 work-hardened in the forging step is punched in the punching step to form the opening portion 3.

The metallic material at the peripheral edge of the opening portion 3 is pushed away radially outward from the radial center to improve the density. This reduces the rollover or the material drag at the peripheral edge of the opening portion 3.

Also, in the striking step (see FIG. 3 ), the striking tool 30 strikes and flattens the small protrusion 6 appearing around the punched opening portion 3. Thus, even if the small protrusion 6 appears in the punching step due to a reason such as a low accuracy in the amount of movement of the punching tool 20 in the slide direction, the small protrusion 6 is struck in the striking step to be flush with the other region of the upper surface 2 c.

As described above, the metalworking apparatus and the metalworking method of the present embodiment reduces the rollover and the material drag and thus improves the exterior quality of the plate-shaped product 4.

The present invention is not limited to the above-described embodiments, and various changes can be made. The above-described embodiments have been exemplarily presented in order to describe the present invention comprehensibly, and is not necessarily limited to an embodiment including all configurations described. Also, a part of a configuration of one embodiment can be replaced with a configuration of another embodiment, and a configuration of one embodiment can be added to a configuration of another embodiment as well. Also, a part of a configuration of each embodiment can be removed, or replaced with or added to another configuration. The above-described embodiments can be changed as below, for example.

The three modifications of the forging tool are presented as shown in FIGS. 9A to 9C in the present embodiments. Meanwhile, a forging tool, a punching tool, and a striking tool are not limited to those of the present embodiment. For example, their distal ends may be in semispherical shapes or the like. A forging tool, a punching tool, and a striking tool are not particularly limited in shape, number, and material as long as they work-harden the to-be-opened portion through forging.

LIST OF REFERENCE SIGNS

-   1 metalworking apparatus -   3 opening portion -   5 to-be-opened portion -   10 forging tool -   16 inner side surface -   20 punching tool -   22 insertion portion -   24 proximal end portion -   26 shoulder portion 

1. A metalworking apparatus comprising: a forging tool configured to work-harden a to-be-opened portion of a workpiece through forging; and a punching tool configured to form an opening portion in the to-be-opened portion by punching, wherein the punching tool has an insertion portion that has a diameter equal to a diameter of the opening portion, and a shoulder portion which is joined to the insertion portion and has a diameter which is larger than a diameter of the insertion portion and increases as the shoulder portion extends toward a proximal end of the punching tool, and wherein when forming the opening portion by punching, the punching tool is inserted to such a position that the shoulder portion contacts a work-hardened portion remaining at an inner peripheral edge of the opening portion from an inner side surface.
 2. The metalworking apparatus according to claim 1, wherein the forging tool has a pressing portion that is provided in a protruding shape and configured to push away the to-be-opened portion radially outward from a radial center.
 3. The metalworking apparatus according to claim 2, wherein the pressing portion has a tapered conical shape.
 4. The metalworking apparatus according to claim 2, wherein, the forging tool has a flat portion which is provided around the pressing portion and configured to come into contact with a peripheral edge of the to-be-opened portion when the to-be-opened portion is forged.
 5. The metalworking apparatus according to claim 1, wherein the shoulder portion of the punching tool has a curved surface which increases in a rate of increase in diameter as the shoulder portion extends toward the proximal end.
 6. The metalworking apparatus according to claim 1, further comprising a striking tool configured to strike and flatten a region surrounding the opening portion while the opening portion is punched, wherein the striking tool has a striking surface that strikes and flattens a small protrusion which appears at a peripheral edge of the opening portion when the shoulder portion of the punching tool is inserted to the insertion portion.
 7. A metalworking method comprising: a forging step of work-hardening a to-be-opened portion of a workpiece through forging; and a punching step of forming an opening portion in the forged to-be-opened portion of the workpiece by punching.
 8. The metalworking method according to claim 7, further comprising a striking step of striking and flatten a small protrusion appearing around the punched opening portion with a striking tool. 